One crucial business mistake I see many games making nowadays is a very specific thing that isn't a bad thing at first glance but is ultimately cancerous to any game's life cycle:
DO NOT ALLOW PLAYERS TO SKIP CONTENT FOR MONEY.
Read that sentence again--aloud. I don't care who's listening in; do it. It's that important.
Let me demonstrate an example of this mistake: World of Warcraft now allows players to buy an instant level up item to jump to level 100 (if I'm not mistaken; I haven't cared to look of late.) This means they instantly skip 99% of the game's content--vanilla, burning crusade, lich king, cataclysm, pandaria...all of it. It's meaningless and unnecessary to them now. This single, simple, subtle mistake has completely obviated almost a DECADE's worth of art, programming, encounter design and storytelling, robbing players of any chance of experiencing the things that ACTUALLY drew people into the Warcraft universe, just so they can "skip to the endgame." Notice how WoW's subscriber base is shrinking? It's because they're plowing through content faster than ever before due to level skips. The design of the game is a big culprit in this, but that's another discussion entirely.
I'll say it again, just because I know it hasn't burned into anyone's eyes yet:
DO NOT ALLOW PLAYERS TO SKIP CONTENT FOR MONEY.
Doing so is nothing more than an admission that you don't care about your work and are ready to simply throw away what you've built in order to cram people into the last 1% of your game. The problem with this is that they then finish the game faster and get bored faster. What do bored players do? They find ways to entertain themselves or move on. This then forces the game to seek new players faster, requiring more expensive advertising, promotions, sales, and -GASP!- more content skips to get them caught up. It's an insidious, inexorable cycle that I've seen destroy games--or at the very least, relegate them to some obscure corner of the web that kids are told to avoid like crime alley.
This can be especially devastating to a subscription based game, since once a player is 'done' he stops paying. Some say retail games care a bit less about this, since the upfront cost is already in the bank, but they still have to move units and that requires new players too. Content skips only hasten the process.
Not only is this foolish from a developer's perspective--since it shows no appreciation for your work, which is now disposable and needs to be recycled ad nauseum for little to no gain--and from a publisher's--since it shortens the profitable lifespan of a game into small bursts that don't stand the test of time--but it's also foolish for a player to take part because, at least in my mind, if you pay for a game, then pay to skip most of it, you have now paid FAR more than the real value of the game to get FAR LESS GAME. If a game promises two hundred hours of fun and you pay to skip 199 of them, what are you paying for???
Frankly, if a game is of a mind to let players skip most of it just to "catch up" then what they're really saying is they don't want people going through the rest of the game--they just want you to start raiding, or PVPing, or...whatever their "endgame" is called. Seems to me they should be charging LESS and instead locking such players out of the rest of the game, since the player isn't getting their money's worth by skipping the game and won't miss the locked parts anyway.
Would you have agreed to pay, say, $5 a month for WoW if the only thing you could do was PVP? My money says a great many people would.